[PATCH 09/16] perf thread-stack: Add thread_stack__sample_late()

From: Adrian Hunter
Date: Wed Apr 01 2020 - 06:18:20 EST


Add a thread stack function to create a call chain for hardware events
where the sample records get created some time after the event occurred.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
tools/perf/util/thread-stack.c | 57 ++++++++++++++++++++++++++++++++++
tools/perf/util/thread-stack.h | 3 ++
2 files changed, 60 insertions(+)

diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
index 0885967d5bc3..83f6c83f5617 100644
--- a/tools/perf/util/thread-stack.c
+++ b/tools/perf/util/thread-stack.c
@@ -497,6 +497,63 @@ void thread_stack__sample(struct thread *thread, int cpu,
chain->nr = i;
}

+/*
+ * Hardware sample records, created some time after the event occurred, need to
+ * have subsequent addresses removed from the call chain.
+ */
+void thread_stack__sample_late(struct thread *thread, int cpu,
+ struct ip_callchain *chain, size_t sz,
+ u64 sample_ip, u64 kernel_start)
+{
+ struct thread_stack *ts = thread__stack(thread, cpu);
+ u64 sample_context = callchain_context(sample_ip, kernel_start);
+ u64 last_context, context, ip;
+ size_t nr = 0, j;
+
+ if (sz < 2) {
+ chain->nr = 0;
+ return;
+ }
+
+ if (!ts)
+ goto out;
+
+ /*
+ * When tracing kernel space, kernel addresses occur at the top of the
+ * call chain after the event occurred but before tracing stopped.
+ * Skip them.
+ */
+ for (j = 1; j <= ts->cnt; j++) {
+ ip = ts->stack[ts->cnt - j].ret_addr;
+ context = callchain_context(ip, kernel_start);
+ if (context == PERF_CONTEXT_USER ||
+ (context == sample_context && ip == sample_ip))
+ break;
+ }
+
+ last_context = sample_ip; /* Use sample_ip as an invalid context */
+
+ for (; nr < sz && j <= ts->cnt; nr++, j++) {
+ ip = ts->stack[ts->cnt - j].ret_addr;
+ context = callchain_context(ip, kernel_start);
+ if (context != last_context) {
+ if (nr >= sz - 1)
+ break;
+ chain->ips[nr++] = context;
+ last_context = context;
+ }
+ chain->ips[nr] = ip;
+ }
+out:
+ if (nr) {
+ chain->nr = nr;
+ } else {
+ chain->ips[0] = sample_context;
+ chain->ips[1] = sample_ip;
+ chain->nr = 2;
+ }
+}
+
struct call_return_processor *
call_return_processor__new(int (*process)(struct call_return *cr, u64 *parent_db_id, void *data),
void *data)
diff --git a/tools/perf/util/thread-stack.h b/tools/perf/util/thread-stack.h
index e1ec5a58f1b2..8962ddc4e1ab 100644
--- a/tools/perf/util/thread-stack.h
+++ b/tools/perf/util/thread-stack.h
@@ -85,6 +85,9 @@ int thread_stack__event(struct thread *thread, int cpu, u32 flags, u64 from_ip,
void thread_stack__set_trace_nr(struct thread *thread, int cpu, u64 trace_nr);
void thread_stack__sample(struct thread *thread, int cpu, struct ip_callchain *chain,
size_t sz, u64 ip, u64 kernel_start);
+void thread_stack__sample_late(struct thread *thread, int cpu,
+ struct ip_callchain *chain, size_t sz, u64 ip,
+ u64 kernel_start);
int thread_stack__flush(struct thread *thread);
void thread_stack__free(struct thread *thread);
size_t thread_stack__depth(struct thread *thread, int cpu);
--
2.17.1